Wet week expected locally

The National Weather Service in Seattle is warning coastal Washington residents that a fall wet weather pattern is developing this week.

According to the weather service, the season’s first active fall weather is expected as a series of Pacific weather systems move across the area.

This will include rain amounts not seen since last spring; some of the greatest amounts are expected along the coast.

Wind speeds will be heavier than we have seen over the past few months, possibly leading to leaves clogging storm drains and gutters as 3-10 inches of rain come down. This could bring local waterways to flood stage and lead to ponding in streets.

While water levels in rivers and streams will rise from their current early fall low levels, major river flooding is not expected.

Ocean swells could reach 20 feet by late Thursday, leading to increased beach erosion and dangerous conditions.

IMPACTS:

* Wind: Blustery winds at times will increase the fallen leaves, which may clog storm drains and gutters.

* Rain: Mountain and coastal areas may see totals of 3 to 10 inches highest over the Olympics this week while the interior lowlands could get up to two inches. ** see attached graphic**

* Rivers: Will rise with a few possibly approaching flood stage.

* Urban Areas/Small Streams: Fallen leaves accumulating around storm drains may lead to ponding of water or local flooding in low spots in urban areas.

* Coastal: Ocean swells may reach 20 feet by late Thursday leading to beach erosion and dangerous beach conditions.

* Mountain Snow: Snow levels will be high, resulting in most precipitation in the mountains being in the form of rain. Precipitation in the passes will generally be in the form of rain this week.

* Timing: Impacts from late Monday through Thursday

SYNOPSIS:

The season’s first active fall weather is anticipated this upcoming week as a series of Pacific weather systems move across the area. The associated weather will include rain amounts not seen since last spring; the greatest amounts are expected in the mountains and along the coast. While water levels in rivers and streams will rise from their current early fall low levels, major river flooding is not expected at this time. Falling leaves from blustery winds may accumulate around storm drains and could lead to ponding of water or local urban flooding. The Pacific weather systems will be “warm storms” with snow levels well over 5000 feet and rain in the passes.

WATCHES/WARNINGS/ADVISORIES:

None at this time.

WHAT WE KNOW NOW:

The first Pacific weather system is likely to arrive late Monday night and Tuesday giving rain and blustery conditions. A stronger system is expected to reach the area late Tuesday night or early Wednesday and give locally heavy rain and windy conditions to the area Wednesday into Wednesday night or Thursday. Ocean swells along the coast are expected to build to above 10 feet on Tuesday and up to as high as 20 feet late Thursday resulting in the potential of significant wave run-up and possible beach erosion. Confidence is high that this will be a wet and windy period.

WHAT IS MOST LIKELY TO EVOLVE:

The location of the heaviest rainfall will be on the Olympic Peninsula, but it isn’t known if the heaviest rainfall in the interior will be in northern or southern portions of Western Washington. The weather systems may move through the area faster or slower than currently expected. The timing and speed of the systems will affect total rainfall amounts. Forecasts will be refined as we move closer to the event. Monitor forecasts and weather statements well into next week.